The invention relates to an electropneumatic double regulating valve for an air-operated vehicle brake system.
The electropneumatic double regulating valve of the present invention is disposed centrally on a wheel axle, equipped with two brakes, with a common relay valve housing, in which is integrated for each brake an assigned regulating valve unit, which comprises for valve actuation a control piston, which can be axially adjusted and is disposed inside an assigned control chamber and which is driven with a control pressure by way of an electromagnetic pilot valve assembly, housed in an adjacent pilot valve housing, for independent axial adjustment, whereby the pilot valve housing is connected detachably to a relay valve housing by way of a sealing arrangement that lies in-between. In particular the present invention relates to a special configuration of this sealing arrangement.
A generic regulating valve is installed inside an air brake system of a vehicle, in order to correct a brake pressure in accordance with the desired braking effect. For this purpose a brake line, issuing from the regulating valve, is usually connected to a brake cylinder on the vehicle wheel. Said brake cylinder produces the brake force, required to brake the vehicle wheel, for a disk or drum brake attached to said wheel. The desired pressure value for the electropneumatic regulating valve can be specified both electrically and pneumatically. However, the pneumatic drive is usually used only for safety in the case that the electric drive fails.
Such an electropneumatic regulating valve is known from the DE 196 05 562 A1. The regulating valve exhibits an internal control piston, which has a large area and is housed inside a control chamber, disposed in the relay valve housing. The control piston separates the control chamber from an opposing working chamber. On the side of the working chamber a coaxial hollow pin, which serves to actuate an adjacent valve seat assembly, is formed on the control piston. The valve seat assembly switches, by means of an axial adjustment of a spring-stressed valve tube, the compressed air flow between an external brake line connection, a feed pressure connection, as well as a venting port. The control chamber is actuated by means of a pilot valve assembly with a control pressure, which acts on a control piston. The pilot valve assembly comprises here two electropneumatic pilot valves, which affect, by means of a coordinated flow around the integrated electric coils, an increase, hold or decrease in the control pressure inside the control chamber, which produces a working pressure for the brake cylinder on the opposite side of the control piston. The pilot valve housing is connected detachably to the relay valve housing by means of a sealing ring, which seals the working chamber in the direction of the atmosphere.
In addition to the above described embodiment of an electropneumatic regulating valve with a single integrated regulating valve unit, the background art also discloses double regulating valves, wherein two regulating valve units are integrated into a common relay valve housing. This configuration is usually used for rear axles of motor vehicles, where a central arrangement on the frame is possible. In this respect the double regulating valve actuates both brakes, assigned to the wheels of the wheel axles.
In casting the common relay valve housing and also the pilot valve housing connected thereto, there is the problem that the exact relative position of both adjacent control chambers cannot be reliably guaranteed. In addition to this casting-induced housing tolerance, the sealing rings that are used are also subject to a tolerance. Consequently the result can be an unfavorable chain of tolerances, so that the tightness between the relay valve housing and the pilot valve housing is not always guaranteed. In addition, individual sealing rings are often forgotten during manual assembly so that the resulting cost of reworking is high.
Therefore; an object of the present invention is to further improve an electropneumatic double regulating valve of the above described kind to the effect that a simple to assemble sealing arrangement is found that guarantees a reliable seal between the relay valve housing and the pilot valve housing.
The problem is solved starting from an electropneumatic double regulating valve disposed centrally on a wheel axle equipped with two brakes, with a common relay valve housing containing a control piston for each brake, each control piston being axially adjustable and driven with a control pressure by way of an electromagnetic pilot valve assembly housed in an adjacent pilot valve housing, whereby the pilot valve housing is connected detachably to the relay valve housing by way of a sealing arrangement that lies in-between,
The problem is solved in one embodiment of the invention, by a one-piece sealing arrangement, comprising two sealing ring segments, which are in essence ring-shaped and are assigned to one control chamber each and which are connected together by means of several footbridges, which are molded on in-between and which are separated from each other in such a manner between the two sealing ring segments that an elastic deformation of the footbridges results in a defined compensation of the tolerance of the relative position of both sealing ring segments in the connecting plane between the pilot valve housing and the relay valve housing.
An advantage of the inventive sealing arrangement lies in the fact that, owing to the individual sealing components being one piece, they cannot be forgotten during assembly. In addition, the one piece design of the sealing arrangement offers ideal conditions for automating the assembly process. The flexibility in spacing the two sealing ring segments makes it easy to compensate for the casting-induced tolerances at the relay valve housing and/or the pilot valve housing. The invention makes it possible to compensate for the tolerances with the elastically flexible footbridges. In this manner the tolerances can be balanced without hardly any force.
According to another embodiment of the invention, at least one of the footbridges is designed relatively rigid and at least one of the footbridges, arranged separately on the opposite side, is designed relatively elastic so that the tolerance is balanced by adjusting the angle of the two sealing ring segments with respect to each other. The result of the rigidly designed footbridge is an easy to manipulate sealing arrangement, which is relatively stable in its one-piece form, whereby the elastic footbridge compensates for the tolerance.
Preferably the footbridges are designed in the shape of an outwardly oriented arch in order to facilitate the deformation. In addition, the footbridges can be formed with a round to oval cross section in order to avoid twisting during deformation.
According to another embodiment of the invention, the two adjacent footbridges can serve together with the neighboring arch members of the sealing ring segments to seal a pressure medium channel running between the pilot valve housing and the relay valve housing. Such a pressure medium channel can be provided, for example, to provide feed pressure from the feed pressure connection at the relay valve housing for the pilot valves, housed in the pilot valve housing. To seal this pressure medium channel, there is no need to provide a separate sealing element.
To guarantee adequate shape stability for the sealing arrangement, the two sealing ring segments, made of an elastic material, and the rigid footbridges can be provided with an internal reinforcing insert, made of a rigid material, like steel, aluminum, or plastic.
Preferably the sealing ring segments comprise a main sealing segment, extending radially in the connecting plane between the pilot valve housing and the relay valve housing, and an external radial sealing segment for a static seal of the housing as well as an internal radial sealing segment for a dynamic seal of the control piston. In addition, in the area of the main sealing segment at least one point on the periphery of the sealing ring segment can exhibit a passage for a valve-internal pressure medium channel, running between the relay valve housing and the pilot valve housing. Such a passage can also be used as a holder for a pressure compensating element, integrated into the sealing arrangement. The pressure compensating element is provided to balance the pressure with the atmosphere for valve-internal areas of the pilot valve housing that are not used as the pressure chamber.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.